What is the relationship between minimum fluidisation velocity and the mean particle size?
The experimental minimum fluidization velocity is about equal to the theoretical for the small particles (100-200 µm). For the larger particles the experimental minimum fluidization velocities are significantly lower than the theoretical.
What are the factors that affect fluidization?
The study focused mainly on four in-line measurements (dependent variables): fluidization parameter (calculated by inlet air flow rate and rotor speed), pressure difference over the upper filters, pressure difference over the granules (lower filter), and temperature of the fluidizing mass.
What are the different types of fluidization?
Based on different Geldart particle groups and gas velocities, several different fluidization regimes can be observed: fixed bed, homogeneous fluidization, bubbling fluidization, slugging fluidization, turbulent fluidization, and entrainment process.
What is the point of minimum fluidisation?
At minimum fluidization the velocity of the solids is taken to be the velocity in the packed bed region, that is, zero. The porosity at minimum fluidization is determined from the height of the bed at minimum fluidization.
Where is fluidization used?
The resulting phenomenon is called fluidization. Fluidized beds are used for several purposes, such as fluidized bed reactors (types of chemical reactors), solids separation, fluid catalytic cracking, fluidized bed combustion, heat or mass transfer or interface modification, such as applying a coating onto solid items.
Why do we use fluidization?
These chemical reactions are highly exothermic and fluidization ensures a uniform temperature, minimizing unwanted side reactions, and efficient heat transfer to cooling tubes, ensuring high productivity.
What is the purpose of fluidization?
Fluidization is defined as a method to keep solid particles floating in an upward direction (Figure 5) in a flow of gas or liquid. In freezing, fluidization occurs when particles of a similar shape and size are subjected to an upward stream of low-temperature air.
Why fluidization is required?
Fluidized beds are used for several purposes, such as fluidized bed reactors (types of chemical reactors), solids separation, fluid catalytic cracking, fluidized bed combustion, heat or mass transfer or interface modification, such as applying a coating onto solid items.
What is the use of fluidization?
Typical food processing applications of fluidization include freezing and cooling, drying, puffing, freeze drying, spray drying, classification and blanching and cooking. These processes involve heat and mass transfer to or from the food material, which can be rapidly achieved from fluidization.
Why is fluidization important?
What is the advantage of fluidization?
The chief advantage of fluidization are that the solid is vigorously agitated by the fluid passing through the bed, and the mixing of the solid ensures that there are practically no temperature gradients in the bed even with quite exothermic or endothermic reactions.
What is fluidized state?
A fluidized bed is a state of a two-phase mixture of particulate solid material and fluid, which is widely used in many modern technologies for efficient implementation of various physical and chemical processes.
Can Wen and Yu relations be used simultaneously for minimum fluidization velocity?
The present study has demonstrated the contradiction deduced from the simultaneous use of these Wen and Yu relations as it is the case for the minimum fluidization velocity.
Why is Wen and Yu correlation important?
A STRANGE CONSEQUENCE OF WEN AND YU CORRELATIONS The Wen and Yu correlation is popular and frequently used in fluidization engineering because it allows us to evaluate the minimum fluidization velocity of a given material with a certain reliability.
What do you think about Wen and Yu’s method?
The method of Wen and Yu which consists of simultaneously eliminating the bed voidage at minimum fluidization and particle sphericity from the minimum fluidization velocity calculation remains definitively scientifically wrong and should be avoided.
Can we predict the onset of fluidisation from Yu’s equation?
Wen and Yu’s equation does not reliably predict the gas velocity for minimum fluidisation. Now the onset of fluidisation can be predicted knowing only the particles’ size and sphericity. A relation is suggested between the voidage at incipient fluidisation and the particles’ sphericity.